converting time from UTC to CST - python-3.x

Question

I am trying to convert UTC time to CST. But I am not getting the output as expected.
Below is my code:
import datetime
import pytz
fmt = '%Y-%m-%d %H:%M:%S %Z%z'
e = pytz.timezone('US/Central')
time_from_utc = datetime.datetime.utcfromtimestamp(int(1607020200))
time_from = time_from_utc.astimezone(e)
time_from.strftime(fmt)
time_to_utc = datetime.datetime.utcfromtimestamp(int(1609785000))
time_to = time_to_utc.astimezone(tz=pytz.timezone('US/Central'))
print(time_from_utc)
print(time_from)
print(time_to_utc)
print(time_to)
Here is the output:
(base) ranjeet#casper:~/Desktop$ python3 ext.py
2020-12-03 18:30:00
2020-12-03 07:00:00-06:00
2021-01-04 18:30:00
2021-01-04 07:00:00-06:00
I was expecting that after conversion, I should get time corresponding to the time of UTC i.e.
2020-12-03 18:30:00
2020-12-03 12:30:00-06:00
since CST is -6 Hours from UTC.
Any help is appreciated.

Answer 1

the problem is that
time_from_utc = datetime.datetime.utcfromtimestamp(int(1607020200))
gives you a naive datetime object - which Python treats as local time by default. Then, in
time_from = time_from_utc.astimezone(e)
things go wrong since time_from_utc is treated as local time. Instead, set UTC explicitly when calling fromtimestamp:
from datetime import datetime, timezone
import pytz
fmt = '%Y-%m-%d %H:%M:%S %Z%z'
e = pytz.timezone('US/Central')
time_from_utc = datetime.fromtimestamp(1607020200, tz=timezone.utc)
time_from = time_from_utc.astimezone(e)
time_from.strftime(fmt)
time_to_utc = datetime.fromtimestamp(1609785000, tz=timezone.utc)
time_to = time_to_utc.astimezone(tz=pytz.timezone('US/Central'))
which will give you
2020-12-03 18:30:00+00:00
2020-12-03 12:30:00-06:00
2021-01-04 18:30:00+00:00
2021-01-04 12:30:00-06:00
Final Remarks: with Python 3.9, you have zoneinfo, so you don't need a third party library for handling of time zones. Example usage.